1. Field of the Invention
This invention relates to erosion control devices such as those used at a construction site to block dirt and other contaminants from entering the water drainage system.
2. Description of Related Art
At construction sites, dams such as rock bags (semi-porous bags filled with rocks) are typically used to filter the flow of water into storm drains, in order to protect the water quality of the bodies of water into which the storm drain flows, and also to prevent unwanted buildup of these contaminants within the drainage system, which could otherwise clog the drainage system.
For example, a number of rock bags may be positioned around a storm drain in order to filter drainage water from the construction site, and to prevent other construction contaminants from entering the storm drain, thereby reducing water pollution and protecting water quality.
In addition to the rock bags, other portable dams and erosion control systems have been developed. For example, straw waddles include a long tubular-shaped sheath of straw that slows and filters drainage water. Commercial products such as the Gutterbuddy™, available from ACF Environmental of Richmond, Va. (www.acfenvironmental.com) include synthetic fibers bundled in a tube. In addition, inlet protection systems such as the FiltR Fence™, also available from ACF Environmental, include a frame that has a screen-like geotextile sleeve that is attached around the frame's perimeter. In that design, the frame can be assembled by securing the frame members to each other with steel pins. The assembled frame is then placed to protect an inlet. The FiltR Fence™ frame can also be taken apart for ease of transportation.
These erosion control systems all have drawbacks. For example, rock bags are heavy, expensive to implement, and/or in practice do not function well to prevent pollution. For example, dirt quickly builds up within the rock bags and the other dams, rendering them effectively useless. Dirt and rocks also build up in front of the bags, eventually blocking the flow of water, all of which can create large puddles of backed-up water. While the proper practice would then be to shovel out the dirt and the backed-up water and replace the non-functional bags, in practice construction workers find it easier to just pick up one or two bags and let the water flow through the open space. Furthermore, in a big rainstorm, the flow of water may be so large and forceful as to simply flow right over the bags.
Optimally, the dirt and rocks that build up in front of the bags should be cleaned regularly in order to ensure proper function. However, the rock bags create a difficult obstacle for street sweeping, and rather than moving the heavy bags and re-positioning them, the street sweeper usually just drives around the bags, leaving the dirt and rock buildup in front of the bags.
In addition, the bags are often damaged when they are run over by heavy equipment at a construction site, and even if they are not damaged, eventually they deteriorate due to effects of weather (e.g., sun and water), all of which limits their effectiveness. Severely damaged or deteriorated bags can spill rock, which actually adds to the problem of construction debris rather than reducing it. And at the end of the construction project, removal and disposal of the rocks and rock bags can require considerable time and expense.
Furthermore, the rock bags at best only filter dirt, sand and large objects such as rocks and gravel. Other contaminants such as oil or smaller particles are not filtered by the rock bags, leaving those contaminants to pollute water supplies and clog drainage systems. Specifically, it would be advantageous to provide a filter that effectively filters particulate matter down to 10 microns, a size small enough to include hydrocarbon excess such as may build up on roads from gas and oil spillage, tire wear, and other motor vehicle usage. Such a filter would prevent such particulate waste from getting into the water system.